Continuous flash point recording



April 29, 1969 L- D. LIVINGSTON ET AL 3,440,863

con'rxuuous FLASH POINT RECORDING Filed July 16. 1965 Sheet I of 2CONTROLLER FIG. l

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1.. o. LIVINGSTON J. K. ROWLAND s. Th. F. CRESPIN MZM THEIR ATTORNEYAPril 1969 D. LIVINGSTON ET AL 3,440,863

CONTINUOUS FLASH POINT RECORDING Filed July 16. 1965 7 Sheet 2 of 2 R 53SPARK FLASH so I B l l l- 1/ 0 I0 20 so 40 so so 10 so so 100 no I20 I50I40 INVENTORS:

L. D. LIVINGSTON J. K. ROWLAND 3 G. Th. F. CRESPIN MZM THEIR ATTORNEYUnited States Patent 2 Claims ABSTRACT OF THE DISCLOSURE An apparatusfor determining the flash oint of a liquid, particularly a liquid havinga flash point higher than about 85 C. The apparatus utilizes a flashchamber having liquid and vapor chambers therein. A heated gas liquidmixture is supplied to the flash chamber, vaporized and ignited. Aseparate heater is used to maintain the temperature of the vapor spaceat the flash point of the liquid.

The invention relates to an instrument for determining the flash pointof a liquid, more particularly, to an instrument for determining andrecording the flash point of a continuous stream of liquid. Further, theinvention concerns a method of controlling a process such as adistillation, dewaxing, an extraction or a deasphalting process, on thebasis of the flash point of a product of this process.

There are disclosed in the prior art various instruments for determiningthe flash point of a hydrocarbon liquid, especially a petroleum product.One instrument of the prior art utilizes in combination a flash chamberand means exterior of said chamber for heating a stream of liquid andfor heating an oxygen-containing gas (e.g., air). The heated liquid andgas are introduced into the flash chamber, and a pool of the liquid ismaintained at a constant or substantially constant level in the saidchamber. An ignition spark is supplied to the flash chamber above thelevel of the pool in the presence of the gas. The temperature of theliquid pool in the flash chamber is measured, and the occurrence of aflash within the chamber is detected. The temperature of the liquid maybe measured automatically upon the occurrence of a flash in the vaporspace of the flash chamber.

The heating means is designed to progressively increase the temperatureof the liquid supplied to the flash chamber with the heating means beingregulated by the said flash detecting means. The instrument will thusmaintain the temperature of the liquid at least substantially at thelevel at which flashing occurs. Thus, the flash point temperature of thestream of liquid may be continually measured in a relatively rapidlyrepetitive way.

The instrument described above is used for measuring the flash points oflight petroleum products, such as gasoline and kerosene, with flashpoints up to about 85 C. It has been found, however, that the knowninstrument is unsuitable for testing liquids with flash points higherthan the said limit, since irregular flashing occurs in experimentscarried out with liquids with such higher flash point temperatures.

It is therefore an object of the present invention to provide aninstrument which is particularly adapted for testing a liquid withrelatively high flash point temperatures, such as a lubricating oildistillate, though it may be used for testing liquids with relativelylow flash point temperatures as well.

The present invention provides an instrument for measuring the flashpoint of liquids that is equipped with im- 3,440,863 Patented Apr. 29,1969 proved heating means for the vapors generated and/or for the liquidto be tested.

In accordance with the first of the said features the instrument isprovided with a separate heating means for the vapor space of the flashor vapor chamber. The vapor chamber is adjacent to and preferablysituated above the liquid chamber. The liquid and vapor chamberstogether form the flash chamber and usually a splash shield (e.g., atray with a bubble cap) is fixed between the two chambers. In thepreferred embodiment of the instrument, control means responsive toflashing detected by the flash detector are utilized for temporarilydecreasing or switching off the separate heating of the vapor chamber.The decrease or the switching off may be effected for a predeterminedtime interval, which may be related (but not necessarily so) to thespark time interval.

The second of the above features concerns the application of a preheaterfor the incoming liquid stream in combination with control meansdependent on the temperature difference across the aforesaid mainheating means of the liquid (or liquid and gas, if they are heatedtogether in the main heater). The temperature difference is maintainedat a constant or at least substantially constant value. In the preferredembodiment of the instrument both features are present simultaneously.

Preferably, the liquid and the gas streams are heated in a combinedheater (saturator) which is close to and integral with the flashchamber. The saturator, which is usually heated inside, e.g., by meansof a cartridge heater, may consist of a helical channel that dischargesinto the liquid chamber.

As already mentioned above, the known instrument for determining theflash point of a liquid is equipped with a. heater arranged forprogressively increasing the temperature of the liquid. A control meansregulated by the flash detector maintains the temperature of the liquidat least substantially at the level at which flashing occurs.

In a preferred embodiment of the present invention the heating isincreased progressively as long as no flashing occurs; as soon asflashing is detected the heating is progressively decreased during theflashing period; when flashing stops the heating is again progressivelyincreased.

When testing or measuring the flash point of liquids with relativelyhigh flash points, the known types of flash detectors have provedunreliable mainly because of the high temperatures occuring in the vaporchamber. A new device has been developed consisting of a housing with adiaphragm, preferably formed of tetrafluoroethylene resin known asTeflon. The diaphragm is subject on one side to the vapor space pressureand on the other to atmospheric pressure.

The occurrence of a pressure wave generated by a flash results in adisplacement of the diaphragm, which is utilized, e.g., mechanicallyoptically or electrically, to generate a signal that may be indicated,recorded and/0r transformed into a control signal. Preferably, the otherside of the diaphragm affects an electrical circuit, e.g., :by actuatinga switch. Normally, the chamber containing the diaphragm is connected tothe vapor space by a short line. The use of a short line prevents thediaphragm from being fouled by the products of combustion produced inthe vapor space.

The instrument measuring the flash point temperature may be used forcontrolling a process on the basis of the flash point of a product ofthat process. A sample stream of the said product is fed to theinstrument, the flash point temperature is measured and a signalcorresponding to the measured temperature is supplied to a controller.The output signal of the controller is used to control the process insuch a Way as to make the product of the process assume at leastapproximately a constant flash point. Alternatively, the control may beeffected to prevent the products flash point from exceeding a givenlimit. Such a control may, inter alia, be applied in propanedeasphalting or asphalt-containing residues and in the extraction, forexample, the furfurol extraction, or in the solvent dewaxing oflubricating oils.

The solvents used have to be removed from the several phases in theseprocesses and the flash point of these phases is a sensitive indicationof the degree of solvent removal. The stripping of the solvents in thephases may be controlled by means of the present instrument in the wayset forth above.

The above features and advantages of this invention will be more easilyunderstood from the following detailed description when taken inconjunction with the attached drawings in which:

FIGURE 1 is an elevation partly in section of one embodiment of thisinvention;

FIGURE 2 is a schematic drawing of a second embodiment of thisinvention; and

FIGURE 3 is a graph of the measured temperature and the operation of theheater with respect to time.

Referring to FIGURE 1 the instrument is built up mainly of two parts: aflash chamber 1, and a heater (saturator) 2 which is close to andintegral with the flash chamber. The flash chamber consists of a liquidchamber 3 and a vapor chamber 4 situated immediately above the liquidchamber. The vapor chamber is provided with spark ignition means 5connected at 6 to a source of high tension voltage or spark generator(not shown). The flash chamber is also provided with an outlet for vapor7. A spark is produced at regular time intervals, e.g. every seconds.Usually a direct current spark is used, but an alternating current sparkmay be applied instead.

The vapor chamber is also connected via a short line 8 with a flashdetector 9. The flash detector 9 consists essentially of a diaphragm 10acting upon an electric switch 1].. The diaphragm is preferably made oftetrafluoroethylene known as Teflon and may have a diameter of about 5inches. Shock waves generated by a flash in the vapor chamber aredetected by the diaphragm which thereupon actuates the switch 11. Theswitch 11 may be either opened or closed by the movement of thediaphrgam 10.

The feed inlet of the liquid to be tested is at 12. Normally liquid issupplied at a fixed or metered rate by means of a constant displacementpump or a metering orifice disposed in the inlet 12. A metered flow ofthe oxygen-containing gas, normally air, is introduced at 13 and mixedwith the liquid before heating in the saturator 2 takes. place. In aspecific case the rate of flow of the liquid (oil) was about 4.5 litersper hour and the rate of flow of the oxygen-containing gas (air) wasabout 14 liters per hour. Of course these flow rates may generally varybetween wide limits, depending on the nature of the liquid to be testedand of the oxygen-containing gas used.

The saturator is built up of a cartridge heater 14 situated inside ahelical channel 15. The heater receives its electrical supply throughterminals 16.

The mixture of liquid and gas flow upward through the helical channel 15and out the exit 17 into the liquid chamber 3. The vapor/liquidseparation takes place by gravity. A splash shield 18 prevents liquiddrops from carrying over into the vapor chamber 4.

The heated liquid forms a pool in the liquid chamber 3. A constant levelof the pool is maintained by providing the liquid outlet through liquidoverflow pipe 19 with a weir 20 A temperature measuring means 21, forexample, a thermocouple, is located in the saturator outlet 17 tomeasure the temperature of the test liquid under test conditions. Themeasured temperature may be displayed on a recorder 22.

According to the invention, the vapor chamber 4 is provided withseparate heating means 23. The separate heating means 23 may be a collarheater with terminals 24 for connection with an electrical power supply.In order to compensate for the heat of combustion generated when thevapor in the vapor chamber flashes, the heat supplied to the heater 23is decreased, preferably switched off, as soon as flashing occurs. Whenflashing stops the heat input to the heater is restored.

According to another feature of the invention, a preheater for theincoming liquid stream is provided in line 12; this preheater isschematically indicated at 25 and its construction may be similar tothat of the saturator, i.e., consist mainly of a housing, a helicalchannel for the liquid and a cartridge heater mounted inside the helicalchannel.

Thus only part of the heat input to the flowing liquid stream isprovided by the saturator unit 2 with the major part being supplied bythe preheater 25. A temperature measuring means 27, for example, athermocouple, is disposed at the inlet to the saturator unit 2. Themeasured temperatures at 21 and 27 are supplied to a controller 26. Thecontroller 26 controls the heat input to the preheater 25 to maintain aconstant temperature differential across the saturator unit 2. The valueof the temperature differential across the saturator unit is set bymeans of the set point 28 on the controller 26. Normally a 15 to 30degree Centigrade temperature differential is satisfactory.

In this manner, the work done by the saturator heater is kept verynearly constant and the instrument is capable of dealing in a stable waywith large disturbances in condition and properties of the liquid to beheated. This is of special advantage when the liquid stream to be testedshows substantial variations in flash point.

The complete instrument is usually housed in an explosion-proof box,that may, but need not, be temperaturecontrolled.

The instrument so far described may be used for testing the flash pointof liquids, e.g. for indicating whether or not a liquid surpasses acertain predetermined flash point temperature. The heating of thesaturator may be controlled (not shown in the figure) in this case insuch a way that the liquid-gas mixture delivered to the flash chamber iscontinuously maintained at the said predetermined temperature.

When the device is used for actual flash point measurement, asdistinguished from merely indicating whether a flash has occurred belowa selected temperature level, the means for heating the liquid arearranged for progressively increasing the temperature of the liquidsupplied to the liquid chamber and additional control means for saidheating means are provided to maintain the temperature of the liquid atleast substantially at the level at which flashing occurs. To this endthe power to cartridge heater 14 is decreased or increased, depending onwhether the vapor in the vapor chamber ignites or not.

The complete control system of the preferred embodiment of theinstrument capable of measuring the flash point temperature isillustrated in FIGURES 2 and 3. In FIGURE 2 the numerical indicationscorrespond to those used in FIGURE 1 although some elements are shown ina simplified form.

The system shown in FIGURE 2 includes all of the elements shown inFIGURE 1 and additional controls for the cartridge heater 14, collarheater 23 and spark 5. The terminal 6 of the spark 5 is connected to adirect current spank source 29. The direct current spark source 29 iscontrolled by means of a motor 30 that is adjusted to cause the source29 to energize the spark 5 once every 10 seconds.

The cartridge heater 14 is controlled by a variable transformer 31driven by a reversible motor 32. The motor 32 should be connected to thevariable transformer through a gear train that provides a slow rotationof the transformer control. A suitable speed would be in the range ofone revolution every forty minutes. In addition, the motor should beadjusted to normally rotate the transformer control to increase thevoltage supplied to the cartridge heater.

The collar heater 23 is connected to a source of power by means ofnormally closed contacts on relay 33. The relay 33 is energized by theflash detector 9 to open the normally closed contact and remainsenergized for a period of 9 seconds. The 9-second period is controlledby a switch 34 that is actuated by the motor 30. The motor 30 closes theswitch 34 at the same time that it actuates the spark source 29. Therelay 33 also contains a second set of contacts that close when therelay is energized. The second set of contacts serve to reverse thedirection of rotation of the motor 32. When the motor 32 reverses thevoltage supplied to the cartridge heater 14 will be reduced.

A direct current spark is generated in the vapor chamber 4 once everyseconds by means of a spark generator 29 connected to terminal 6. If thetest liquid is below its flash point, no ignition occurs and the heatinput to the cartridge heater 14 is gradually increased by the variabletransformer 31. As soon as flashing starts the flash detector 9energizes a relay 33. This relay is held in the energized state for aperiod of 9 seconds, determined by a switch 34 actuated by the samemotor 30 which initiates the spark generator. The relay 33 carriescontacts which for the said period of 9 seconds reverse the variabletransformer drive motor 32 and switch off the heating of the collarheater 23. After the period of 9 seconds the relay is de-energized, thecollar heater is switched on and the variac drive is reversed. Onesecond later a new spark is generated and, if another flash shouldoccur, the process just described will be repeated.

FIGURE 3 shows a horizontal time scale 35 running from 0-140 seconds. Itis assumed that the first six and the last two sparks give rise toflashing (indicated by short vertical lines).

The two lines under the time scale represent schematically the conditionof the vapor chamber collar heater 23 (upper line 36) and of thecartridge heater 14 (lower line 37) respectively.

The heater 23 is either in the on or in the off position. From the 60thto the 130th seconds the heater is continuously on.

Line 37 shows the movement of the variable transformer drive motor; fromthe start to the 60th second the variac output voltage is decreasedcontinuously with the exception of the one-second periods at the end ofeach time interval of 10 seconds between two successive sparks.

From the 60th to the 130th second the output voltage is continuouslyincreased.

The temperature as measured by the thermocouple 21 and recorded on therecorder 22 will be the flash point of the liquid being tested. Bycontinuously obtaining a large number of flash points of the liquid andthe average temperature can be determined. The average temperature willacurately reflect the true flash point of the liquid.

We claim as our invention:

1. An instrument for measuring the flash point of a liquid comprising:

a flash chamber including a liquid chamber and a vapor chamber adjacentto and situated above the liquid chamber;

a spark means disposed within said vapor chamber;

flash detecting means in communication with the flash chamber fordetecting a flash occurring within the flash chamber;

aliquid supply means for said flash chamber, an oxygen containing gassupply means, said oxygen supply means communicating vvith said liquidsupply means to supply an oxygen liquid mixture to said flash chamber;

a preheater means, at least said liquid supply means passing throughsaid preheater;

a first heating means, said oxygen liquid mixture passing through saidfirst heating means, said first heating means discharging into theliquid chamber of said flash chamber;

a first temperature measuring means, said first temperature measuringmeans being disposed to measure the temperature of the oxygen liquidmixture at the inlet to said first heating means;

flow control means communicating with said liquid chamber formaintaining a constant liquid level in said liquid chamber;

a second temperature measuring means, said temperature measuring meansbeing disposed to measure the temperature of the liquid in said liquidchamber;

a first control means, said first and second temperature measuring meansbeing coupled to said first control means, said first control meansbeing coupled to said preheater to maintain a constant temperature riseacross said first heating means;

a second heating means, said second heating means being disposed to heatthe vapor in said vapor chamber;

a second control means, said second control means being coupled to saidflash detecting means, and said first and second heating means, saidcontrol means being responsive to said flash detecting means to controlsaid first and second heating means to maintain the liquid in saidliquid chamber and the vapor in said vapor chamber at substantially theflash temperature of the liquid.

2. The instrument of claim 1 wherein said second control meansprogressively decreases the heat input to the first heating means inresponse to flashing detected by said flash detecting means.

References Cited UNITED STATES PATENTS 2,746,285 5/1956 Greanias 73-362,746,286 5/1956 Greanias 7336 2,971,370 2/1961 Jacobs 7336 3,186,2136/1965 Donnell 73--36 3,293,905 12/1966 Ratway et al. 7336 JAMES J.GILL, Primary Examiner.

50 R. S. SALZMAN, Assistant Examiner.

